Consider data on U.S. refrigerator sales from 2009. the market shares of the top 4 firms was 12% for Sears, 9% for lowes. 5% for walmart and 3.5% for home depot. firms 5 through 25 combined summed to 20.5 % and all other independents outside the top 25 sell firms comprised the other 50% industry sales. what is the 4-firms concentration ration for this industry?